The optimization of complex design problems and the mitigation of design's susceptibility to variation continue to present challenges to engineering professionals. Such design challenges are known, for example, from fuel efficiency improvement efforts in motor vehicles, electronic circuit design downscaling in microelectronics, as well as speed improvements and power reductions for consumer electronic devices, among many others. With respect to electronic circuits in general, and with respect to integrated circuits specifically, designers are often concerned with their selection of design components, design component dimensions, impact from global variations, and impact from local variations. Therefore, the subject matter of this invention relates to “Design components”, “Design component dimensions”, “Design component dimension values”, “Global Variation”, and “Local Variation.” Specifically, the subject matter of this invention relates to how to identify and size these key design components and dimensions and how to mitigate global and local variation.
Design components are the components which make up a product. For microelectronics, the design components are circuit elements, e.g., resistors, capacitors, inductors, diodes, transistors, or other solid state devices. These design components are referred to in the description below as “devices.” The design dimensions of an integrated circuit are the dimensions and/or materials an engineer selects and has governing authority over. The global variation of an integrated circuit results from the tolerances of the manufacturing process or operating environment, which may impact the integrated circuit as a whole. In contrast, the local variation of an integrated circuit results from random fluctuations, which occur in integrated circuit fabrication. Such local variation cannot necessarily be addressed directly by adjusting manufacturing tolerance controls.
A traditional approach to design optimization relies on the experience of a designer in knowing in which process-voltage-temperature (PVT) corner an integrated circuit exhibits the worst case behavior. In this regard, some designers rely on general knowledge, for example, that integrated circuits often behave worst in a PVT corner, where the process is slowest, the voltage is lowest, and the temperature is highest. However, not only is this assumption not necessarily always true, but also one should simultaneously consider how design metrics are affected by variability in each process corner. Further, in the traditional design approach it is assumed that the designer has knowledge of which devices, device parameters, and parameter ranges are the main contributors to design metric variation in the integrated circuit. In addition, a designer using the traditional design approach only modifies one dimension at a time; however, every part of an integrated circuit may have unique sensitivity to PVT variation.